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package/znc: add patch for CVE-2026-82373

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This fixes the following vulnerability:

CVE-2026-82373: Use-after-free when unloading modules, triggered by
unprivileged users

Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>
(alternative to commit 43558e103b)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>
This commit is contained in:
Titouan Christophe
2026-09-15 11:28:14 +02:00
committed by Thomas Perale
parent 592df64b46
commit bef43a2af1
2 changed files with 500 additions and 0 deletions
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497
package/znc/0001-fix-crash-while-unloading-modules.patch Normal file
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@@ -0,0 +1,497 @@
From: Alexey Sokolov <alexey+znc@asokolov.org>
Date: Sat, 5 Sep 2026 23:09:25 +0100
Subject: Fix crash while unloading modules
The bug allowed unprivileged users to trigger use-after-free while
unloading modules
Note that the fix requires a slight API change for OnEmbeddedWebRequest:
now the callers (webadmin is the only known caller of it) call it via
DoEmbeddedWebRequest() instead. The modules which implement this hook
need no changes.
CVE-2026-82373
Found by Claude from Anthropic, reported by Ada Logics.
---
Upstream: https://github.com/znc/znc/commit/4b88c64c6e8df29c73568ae1c8b35d797bfa509a
CVE: CVE-2026-82373
Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>
---
include/znc/Modules.h | 71 ++++++++++++++++++++-
include/znc/main.h | 30 ++-------
modules/modperl/functions.in | 2 +-
modules/modpython/functions.in | 2 +-
modules/webadmin.cpp | 12 ++--
src/Client.cpp | 29 +++------
src/Modules.cpp | 112 +++++++++++++++------------------
7 files changed, 145 insertions(+), 113 deletions(-)
diff --git a/include/znc/Modules.h b/include/znc/Modules.h
index ec8b36f883..d842390675 100644
--- a/include/znc/Modules.h
+++ b/include/znc/Modules.h
@@ -465,6 +465,9 @@ class CModule {
void SetNetwork(CIRCNetwork* pNetwork);
void SetClient(CClient* pClient);
+ /** True if the module can be safely unloaded. */
+ bool IsCallStackEmpty() const;
+
/** This function throws CModule::UNLOAD which causes this module to be unloaded.
*/
void Unload() { throw UNLOAD; }
@@ -535,9 +538,11 @@ class CModule {
* @return The List.
*/
virtual VWebSubPages& GetSubPages() { return m_vSubPages; }
+ private:
/** Using this hook, module can embed web stuff directly to different places.
- * This method is called whenever embededded modules I/O happens.
+ * This method is called whenever embedded modules I/O happens.
* Name of used .tmpl file (if any) is up to caller.
+ * Callers call it via `DoEmbeddedWebRequest()`.
* @param WebSock Socket for web connection, don't do bad things with it.
* @param sPageName Describes the place where web stuff is embedded to.
* @param Tmpl Template. Depending on context, you can do various stuff with it.
@@ -547,6 +552,9 @@ class CModule {
virtual bool OnEmbeddedWebRequest(CWebSock& WebSock,
const CString& sPageName,
CTemplate& Tmpl);
+ public:
+ bool DoEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName,
+ CTemplate& Tmpl);
/** Called just before znc.conf is rehashed */
virtual void OnPreRehash();
@@ -1528,6 +1536,9 @@ class CModule {
m_mssRegistry; //!< way to save name/value pairs. Note there is no encryption involved in this
VWebSubPages m_vSubPages;
std::map<CString, CModCommand> m_mCommands;
+ int m_iCallStackDepth = 0;
+
+ friend struct CModCallProtector;
};
class CModules : public std::vector<CModule*>, private CCoreTranslationMixin {
@@ -1766,4 +1777,62 @@ class CModules : public std::vector<CModule*>, private CCoreTranslationMixin {
CClient* m_pClient;
};
+struct CModCallProtector {
+ explicit CModCallProtector(CModule& pMod) : m_pMod(&pMod) {
+ pMod.m_iCallStackDepth++;
+ }
+ ~CModCallProtector() { m_pMod->m_iCallStackDepth--; }
+
+ CModule* m_pMod;
+};
+
+#ifndef SWIG
+template <typename T, T* (CModule::*Getter)() const, void (CModule::*Setter)(T*)>
+struct CTemporaryModField {
+ CTemporaryModField(CModule& pMod, T* pValue) {
+ m_pMod = &pMod;
+ m_pOldT = (pMod.*Getter)();
+ if (pValue) {
+ (pMod.*Setter)(pValue);
+ }
+ }
+
+ ~CTemporaryModField() { (m_pMod->*Setter)(m_pOldT); }
+
+ CModule* m_pMod;
+ T* m_pOldT;
+};
+
+using CTemporaryModClient =
+ CTemporaryModField<CClient, &CModule::GetClient, &CModule::SetClient>;
+using CTemporaryModNetwork =
+ CTemporaryModField<CIRCNetwork, &CModule::GetNetwork, &CModule::SetNetwork>;
+using CTemporaryModUser =
+ CTemporaryModField<CUser, &CModule::GetUser, &CModule::SetUser>;
+
+// Same as above, but for plural CModules
+template <typename T, T* (CModules::*Getter)() const, void (CModules::*Setter)(T*)>
+struct CTemporaryModsField {
+ CTemporaryModsField(CModules& pMods, T* pValue) {
+ m_pMods = &pMods;
+ m_pOldT = (pMods.*Getter)();
+ if (pValue) {
+ (pMods.*Setter)(pValue);
+ }
+ }
+
+ ~CTemporaryModsField() { (m_pMods->*Setter)(m_pOldT); }
+
+ CModules* m_pMods;
+ T* m_pOldT;
+};
+
+using CTemporaryModsClient =
+ CTemporaryModsField<CClient, &CModules::GetClient, &CModules::SetClient>;
+using CTemporaryModsNetwork =
+ CTemporaryModsField<CIRCNetwork, &CModules::GetNetwork, &CModules::SetNetwork>;
+using CTemporaryModsUser =
+ CTemporaryModsField<CUser, &CModules::GetUser, &CModules::SetUser>;
+#endif
+
#endif // !ZNC_MODULES_H
diff --git a/include/znc/main.h b/include/znc/main.h
index 7d22fd43d4..28924d2c02 100644
--- a/include/znc/main.h
+++ b/include/znc/main.h
@@ -56,21 +56,12 @@ extern bool ZNC_NO_NEED_TO_DO_ANYTHING_ON_MODULE_CALL_EXITER;
#define _GLOBALMODULECALL(macFUNC, macUSER, macNETWORK, macCLIENT, macEXITER) \
do { \
CModules& GMods = CZNC::Get().GetModules(); \
- CUser* pOldGUser = GMods.GetUser(); \
- CIRCNetwork* pOldGNetwork = GMods.GetNetwork(); \
- CClient* pOldGClient = GMods.GetClient(); \
- GMods.SetUser(macUSER); \
- GMods.SetNetwork(macNETWORK); \
- GMods.SetClient(macCLIENT); \
+ CTemporaryModsUser TempUser(GMods, macUSER); \
+ CTemporaryModsNetwork TempNetwork(GMods, macNETWORK); \
+ CTemporaryModsClient TempClient(GMods, macCLIENT); \
if (GMods.macFUNC) { \
- GMods.SetUser(pOldGUser); \
- GMods.SetNetwork(pOldGNetwork); \
- GMods.SetClient(pOldGClient); \
*macEXITER = true; \
} \
- GMods.SetUser(pOldGUser); \
- GMods.SetNetwork(pOldGNetwork); \
- GMods.SetClient(pOldGClient); \
} while (false)
#define _USERMODULECALL(macFUNC, macUSER, macNETWORK, macCLIENT, macEXITER) \
@@ -84,17 +75,11 @@ extern bool ZNC_NO_NEED_TO_DO_ANYTHING_ON_MODULE_CALL_EXITER;
} \
if (macUSER != nullptr) { \
CModules& UMods = macUSER->GetModules(); \
- CIRCNetwork* pOldUNetwork = UMods.GetNetwork(); \
- CClient* pOldUClient = UMods.GetClient(); \
- UMods.SetNetwork(macNETWORK); \
- UMods.SetClient(macCLIENT); \
+ CTemporaryModsNetwork TempNetwork(UMods, macNETWORK); \
+ CTemporaryModsClient TempClient(UMods, macCLIENT); \
if (UMods.macFUNC) { \
- UMods.SetNetwork(pOldUNetwork); \
- UMods.SetClient(pOldUClient); \
*macEXITER = true; \
} \
- UMods.SetNetwork(pOldUNetwork); \
- UMods.SetClient(pOldUClient); \
} \
} while (false)
@@ -109,13 +94,10 @@ extern bool ZNC_NO_NEED_TO_DO_ANYTHING_ON_MODULE_CALL_EXITER;
} \
if (macNETWORK != nullptr) { \
CModules& NMods = macNETWORK->GetModules(); \
- CClient* pOldNClient = NMods.GetClient(); \
- NMods.SetClient(macCLIENT); \
+ CTemporaryModsClient TempClient(NMods, macCLIENT); \
if (NMods.macFUNC) { \
- NMods.SetClient(pOldNClient); \
*macEXITER = true; \
} \
- NMods.SetClient(pOldNClient); \
} \
} while (false)
diff --git a/modules/modperl/functions.in b/modules/modperl/functions.in
index a44c818a62..bfa671191c 100644
--- a/modules/modperl/functions.in
+++ b/modules/modperl/functions.in
@@ -66,7 +66,7 @@ void OnServerCapResult(const CString& sCap, bool bSuccess)
void OnClientAttached()
void OnClientDetached()
EModRet OnTimerAutoJoin(CChan& Channel)
-bool OnEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName, CTemplate& Tmpl)
+bool OnEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName, CTemplate& Tmpl)=false
EModRet OnAddNetwork(CIRCNetwork& Network, CString& sErrorRet)
EModRet OnDeleteNetwork(CIRCNetwork& Network)
EModRet OnSendToClient(CString& sLine, CClient& Client)
diff --git a/modules/modpython/functions.in b/modules/modpython/functions.in
index 76ed437a2c..d2914f9dad 100644
--- a/modules/modpython/functions.in
+++ b/modules/modpython/functions.in
@@ -66,7 +66,7 @@ void OnServerCapResult(const CString& sCap, bool bSuccess)
void OnClientAttached()
void OnClientDetached()
EModRet OnTimerAutoJoin(CChan& Channel)
-bool OnEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName, CTemplate& Tmpl)
+bool OnEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName, CTemplate& Tmpl)=false
EModRet OnAddNetwork(CIRCNetwork& Network, CString& sErrorRet)
EModRet OnDeleteNetwork(CIRCNetwork& Network)
EModRet OnSendToClient(CString& sLine, CClient& Client)
diff --git a/modules/webadmin.cpp b/modules/webadmin.cpp
index 0b72413813..ac77517c11 100644
--- a/modules/webadmin.cpp
+++ b/modules/webadmin.cpp
@@ -742,7 +742,7 @@ class CWebAdminMod : public CModule {
CTemplate& mod = Tmpl.AddRow("EmbeddedModuleLoop");
mod.insert(Tmpl.begin(), Tmpl.end());
mod["WebadminAction"] = "display";
- if ((*i)->OnEmbeddedWebRequest(WebSock, "webadmin/channel",
+ if ((*i)->DoEmbeddedWebRequest(WebSock, "webadmin/channel",
mod)) {
mod["Embed"] = WebSock.FindTmpl(*i, "WebadminChan.tmpl");
mod["ModName"] = (*i)->GetModName();
@@ -816,7 +816,7 @@ class CWebAdminMod : public CModule {
TmplMod["ChanName"] = pChan->GetName();
TmplMod["WebadminAction"] = "change";
FOR_EACH_MODULE(it, pNetwork) {
- (*it)->OnEmbeddedWebRequest(WebSock, "webadmin/channel", TmplMod);
+ (*it)->DoEmbeddedWebRequest(WebSock, "webadmin/channel", TmplMod);
}
if (!CZNC::Get().WriteConfig()) {
@@ -1027,7 +1027,7 @@ class CWebAdminMod : public CModule {
CTemplate& mod = Tmpl.AddRow("EmbeddedModuleLoop");
mod.insert(Tmpl.begin(), Tmpl.end());
mod["WebadminAction"] = "display";
- if ((*i)->OnEmbeddedWebRequest(WebSock, "webadmin/network",
+ if ((*i)->DoEmbeddedWebRequest(WebSock, "webadmin/network",
mod)) {
mod["Embed"] = WebSock.FindTmpl(*i, "WebadminNetwork.tmpl");
mod["ModName"] = (*i)->GetModName();
@@ -1246,7 +1246,7 @@ class CWebAdminMod : public CModule {
TmplMod["Name"] = pNetwork->GetName();
TmplMod["WebadminAction"] = "change";
FOR_EACH_MODULE(it, make_pair(pUser, pNetwork)) {
- (*it)->OnEmbeddedWebRequest(WebSock, "webadmin/network", TmplMod);
+ (*it)->DoEmbeddedWebRequest(WebSock, "webadmin/network", TmplMod);
}
if (!CZNC::Get().WriteConfig()) {
@@ -1670,7 +1670,7 @@ class CWebAdminMod : public CModule {
CTemplate& mod = Tmpl.AddRow("EmbeddedModuleLoop");
mod.insert(Tmpl.begin(), Tmpl.end());
mod["WebadminAction"] = "display";
- if ((*i)->OnEmbeddedWebRequest(WebSock, "webadmin/user", mod)) {
+ if ((*i)->DoEmbeddedWebRequest(WebSock, "webadmin/user", mod)) {
mod["Embed"] = WebSock.FindTmpl(*i, "WebadminUser.tmpl");
mod["ModName"] = (*i)->GetModName();
}
@@ -1731,7 +1731,7 @@ class CWebAdminMod : public CModule {
TmplMod["Username"] = sUsername;
TmplMod["WebadminAction"] = "change";
FOR_EACH_MODULE(it, pUser) {
- (*it)->OnEmbeddedWebRequest(WebSock, "webadmin/user", TmplMod);
+ (*it)->DoEmbeddedWebRequest(WebSock, "webadmin/user", TmplMod);
}
if (!CZNC::Get().WriteConfig()) {
diff --git a/src/Client.cpp b/src/Client.cpp
index 0f60f9a11c..db1ec7a62e 100644
--- a/src/Client.cpp
+++ b/src/Client.cpp
@@ -21,8 +21,8 @@
#include <znc/IRCNetwork.h>
#include <znc/Query.h>
-using std::set;
using std::map;
+using std::set;
using std::vector;
#define CALLMOD(MOD, CLIENT, USER, NETWORK, FUNC) \
@@ -30,10 +30,9 @@ using std::vector;
CModule* pModule = nullptr; \
if (NETWORK && (pModule = (NETWORK)->GetModules().FindModule(MOD))) { \
try { \
- CClient* pOldClient = pModule->GetClient(); \
- pModule->SetClient(CLIENT); \
+ CModCallProtector Inside(*pModule); \
+ CTemporaryModClient TempClient(*pModule, CLIENT); \
pModule->FUNC; \
- pModule->SetClient(pOldClient); \
} catch (const CModule::EModException& e) { \
if (e == CModule::UNLOAD) { \
(NETWORK)->GetModules().UnloadModule(MOD); \
@@ -41,13 +40,10 @@ using std::vector;
} \
} else if ((pModule = (USER)->GetModules().FindModule(MOD))) { \
try { \
- CClient* pOldClient = pModule->GetClient(); \
- CIRCNetwork* pOldNetwork = pModule->GetNetwork(); \
- pModule->SetClient(CLIENT); \
- pModule->SetNetwork(NETWORK); \
+ CModCallProtector Inside(*pModule); \
+ CTemporaryModClient TempClient(*pModule, CLIENT); \
+ CTemporaryModNetwork TempNetwork(*pModule, NETWORK); \
pModule->FUNC; \
- pModule->SetClient(pOldClient); \
- pModule->SetNetwork(pOldNetwork); \
} catch (const CModule::EModException& e) { \
if (e == CModule::UNLOAD) { \
(USER)->GetModules().UnloadModule(MOD); \
@@ -55,16 +51,11 @@ using std::vector;
} \
} else if ((pModule = CZNC::Get().GetModules().FindModule(MOD))) { \
try { \
- CClient* pOldClient = pModule->GetClient(); \
- CIRCNetwork* pOldNetwork = pModule->GetNetwork(); \
- CUser* pOldUser = pModule->GetUser(); \
- pModule->SetClient(CLIENT); \
- pModule->SetNetwork(NETWORK); \
- pModule->SetUser(USER); \
+ CModCallProtector Inside(*pModule); \
+ CTemporaryModClient TempClient(*pModule, CLIENT); \
+ CTemporaryModNetwork TempNetwork(*pModule, NETWORK); \
+ CTemporaryModUser TempUser(*pModule, USER); \
pModule->FUNC; \
- pModule->SetClient(pOldClient); \
- pModule->SetNetwork(pOldNetwork); \
- pModule->SetUser(pOldUser); \
} catch (const CModule::EModException& e) { \
if (e == CModule::UNLOAD) { \
CZNC::Get().GetModules().UnloadModule(MOD); \
diff --git a/src/Modules.cpp b/src/Modules.cpp
index d553cbb794..2c4c056fa1 100644
--- a/src/Modules.cpp
+++ b/src/Modules.cpp
@@ -36,67 +36,45 @@ bool ZNC_NO_NEED_TO_DO_ANYTHING_ON_MODULE_CALL_EXITER;
#warning "your crap box doesn't define RTLD_LOCAL !?"
#endif
-#define MODUNLOADCHK(func) \
- for (CModule * pMod : *this) { \
- try { \
- CClient* pOldClient = pMod->GetClient(); \
- pMod->SetClient(m_pClient); \
- CUser* pOldUser = nullptr; \
- if (m_pUser) { \
- pOldUser = pMod->GetUser(); \
- pMod->SetUser(m_pUser); \
- } \
- CIRCNetwork* pNetwork = nullptr; \
- if (m_pNetwork) { \
- pNetwork = pMod->GetNetwork(); \
- pMod->SetNetwork(m_pNetwork); \
- } \
- pMod->func; \
- if (m_pUser) pMod->SetUser(pOldUser); \
- if (m_pNetwork) pMod->SetNetwork(pNetwork); \
- pMod->SetClient(pOldClient); \
- } catch (const CModule::EModException& e) { \
- if (e == CModule::UNLOAD) { \
- UnloadModule(pMod->GetModName()); \
- } \
- } \
- }
-
-#define MODHALTCHK(func) \
- bool bHaltCore = false; \
- for (CModule * pMod : *this) { \
- try { \
- CModule::EModRet e = CModule::CONTINUE; \
- CClient* pOldClient = pMod->GetClient(); \
- pMod->SetClient(m_pClient); \
- CUser* pOldUser = nullptr; \
- if (m_pUser) { \
- pOldUser = pMod->GetUser(); \
- pMod->SetUser(m_pUser); \
- } \
- CIRCNetwork* pNetwork = nullptr; \
- if (m_pNetwork) { \
- pNetwork = pMod->GetNetwork(); \
- pMod->SetNetwork(m_pNetwork); \
- } \
- e = pMod->func; \
- if (m_pUser) pMod->SetUser(pOldUser); \
- if (m_pNetwork) pMod->SetNetwork(pNetwork); \
- pMod->SetClient(pOldClient); \
- if (e == CModule::HALTMODS) { \
- break; \
- } else if (e == CModule::HALTCORE) { \
- bHaltCore = true; \
- } else if (e == CModule::HALT) { \
- bHaltCore = true; \
- break; \
- } \
- } catch (const CModule::EModException& e) { \
- if (e == CModule::UNLOAD) { \
- UnloadModule(pMod->GetModName()); \
- } \
- } \
- } \
+#define MODUNLOADCHK(func) \
+ for (CModule* pMod : *this) { \
+ try { \
+ CModCallProtector inside(*pMod); \
+ CTemporaryModClient TempClient(*pMod, m_pClient); \
+ CTemporaryModUser TempUser(*pMod, m_pUser); \
+ CTemporaryModNetwork TempNetwork(*pMod, m_pNetwork); \
+ pMod->func; \
+ } catch (const CModule::EModException& e) { \
+ if (e == CModule::UNLOAD) { \
+ UnloadModule(pMod->GetModName()); \
+ } \
+ } \
+ }
+
+#define MODHALTCHK(func) \
+ bool bHaltCore = false; \
+ for (CModule* pMod : *this) { \
+ try { \
+ CModCallProtector inside(*pMod); \
+ CModule::EModRet e = CModule::CONTINUE; \
+ CTemporaryModClient TempClient(*pMod, m_pClient); \
+ CTemporaryModUser TempUser(*pMod, m_pUser); \
+ CTemporaryModNetwork TempNetwork(*pMod, m_pNetwork); \
+ e = pMod->func; \
+ if (e == CModule::HALTMODS) { \
+ break; \
+ } else if (e == CModule::HALTCORE) { \
+ bHaltCore = true; \
+ } else if (e == CModule::HALT) { \
+ bHaltCore = true; \
+ break; \
+ } \
+ } catch (const CModule::EModException& e) { \
+ if (e == CModule::UNLOAD) { \
+ UnloadModule(pMod->GetModName()); \
+ } \
+ } \
+ } \
return bHaltCore;
/////////////////// Timer ///////////////////
@@ -205,6 +183,8 @@ void CModule::SetUser(CUser* pUser) { m_pUser = pUser; }
void CModule::SetNetwork(CIRCNetwork* pNetwork) { m_pNetwork = pNetwork; }
void CModule::SetClient(CClient* pClient) { m_pClient = pClient; }
+bool CModule::IsCallStackEmpty() const { return m_iCallStackDepth == 0; }
+
CString CModule::ExpandString(const CString& sStr) const {
CString sRet;
return ExpandString(sStr, sRet);
@@ -622,6 +602,11 @@ bool CModule::OnEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName,
CTemplate& Tmpl) {
return false;
}
+bool CModule::DoEmbeddedWebRequest(CWebSock& WebSock, const CString& sPageName,
+ CTemplate& Tmpl) {
+ CModCallProtector inside(*this);
+ return OnEmbeddedWebRequest(WebSock, sPageName, Tmpl);
+}
// !Webmods
bool CModule::OnLoad(const CString& sArgs, CString& sMessage) {
@@ -1953,6 +1938,11 @@ bool CModules::UnloadModule(const CString& sModule, CString& sRetMsg) {
return false;
}
+ if (!pModule->IsCallStackEmpty()) {
+ sRetMsg = t_f("Module [{1}] is being called, cannot unload.")(sMod);
+ return false;
+ }
+
bool bSuccess;
bool bHandled = false;
_GLOBALMODULECALL(OnModuleUnloading(pModule, bSuccess, sRetMsg),

3
package/znc/znc.mk
View File

@@ -12,6 +12,9 @@ ZNC_CPE_ID_VENDOR = znc
ZNC_DEPENDENCIES = host-pkgconf ZNC_DEPENDENCIES = host-pkgconf
ZNC_CONF_OPTS = -DWANT_CYRUS=OFF -DWANT_I18N=OFF -DWANT_PERL=OFF ZNC_CONF_OPTS = -DWANT_CYRUS=OFF -DWANT_I18N=OFF -DWANT_PERL=OFF
# 0001-fix-crash-while-unloading-modules.patch
ZNC_IGNORE_CVES += CVE-2026-82373
ifeq ($(BR2_PACKAGE_ICU),y) ifeq ($(BR2_PACKAGE_ICU),y)
ZNC_DEPENDENCIES += icu ZNC_DEPENDENCIES += icu
ZNC_CONF_OPTS += -DWANT_ICU=ON ZNC_CONF_OPTS += -DWANT_ICU=ON