libgit2: Inverted IP SubjectAltName Comparison in OpenSSL Backend
libgit2 · libgit2
6.5MediumCVSS 3.1
Recommended action
Within 7 days
Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Patch available
Distribution package intelligence
Ubuntu vendor package status
Canonical’s release and source-package findings are shown separately from local repository availability.
1 package state
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
Ubuntu release
Source package
Vendor state
Fixed version
Evidence
Ubuntu 24.04 LTSnoble · standard archive
libgit2
Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
1 current
CVE-2026-53583 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitylibgit2: libgit2: Network attacker can intercept HTTPS connections via inverted IP SubjectAltName comparison
37 known affected
The vendor explicitly identifies these products as affected by this CVE.
cargo as a component of Red Hat Enterprise Linux 10
clippy as a component of Red Hat Enterprise Linux 10
rust-analyzer as a component of Red Hat Enterprise Linux 10
rust-debugger-common as a component of Red Hat Enterprise Linux 10
rust-doc as a component of Red Hat Enterprise Linux 10
rust-gdb as a component of Red Hat Enterprise Linux 10
rust-lldb as a component of Red Hat Enterprise Linux 10
rust-src as a component of Red Hat Enterprise Linux 10
rust-std-static as a component of Red Hat Enterprise Linux 10
rust-std-static-aarch64-unknown-none-softfloat as a component of Red Hat Enterprise Linux 10
rust-std-static-wasm32-unknown-unknown as a component of Red Hat Enterprise Linux 10
rust-std-static-wasm32-wasip1 as a component of Red Hat Enterprise Linux 10
Summary
A flaw was found in libgit2, a C library for Git functionality. An inverted comparison in the OpenSSL backend's certificate verification logic, specifically when handling IP-literal hosts and certificate IP SubjectAltNames, allows a network attacker to intercept HTTPS connections. By presenting a CA-trusted certificate with any IP SubjectAltName, an attacker can trick libgit2 into accepting a mismatched IP address, leading to the interception of sensitive communication.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Optional official sources
National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.
Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.
Official European source
ENISA European Vulnerability Database
Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.
1 current
ENISA EUVD identifier
EUVD-2026-63549
No EUVD known-exploited evidence
libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.
EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
6.5 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days
Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Patch available
01
What, why and how
libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.
What
libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.
Why
The product does not validate, or incorrectly validates, a certificate.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.
Why
The product does not validate, or incorrectly validates, a certificate.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No confirmed evidence
No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.Reference recorded
CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.
Likely attack path
a network path → Improper Certificate Validation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness ?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-295: Improper Certificate Validation. The product does not validate, or incorrectly validates, a certificate.
CVSS vector ?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
Only matched European and national findings are included. Language selectors and unavailable sources are omitted.
ENISA EUVD · EUVD-2026-63549Official EUVD mapping
libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.
Operational remediation based on structured source evidence.
Status ?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
cargo as a component of Red Hat Enterprise Linux 10; clippy as a component of Red Hat Enterprise Linux 10; rust-analyzer as a component of Red Hat Enterprise Linux 10; rust-debugger-common as a component of Red Hat Enterprise Linux 10; rust-doc as a component of Red Hat Enterprise Linux 10; rust-gdb as a component of Red Hat Enterprise Linux 10; rust-lldb as a component of Red Hat Enterprise Linux 10; rust-src as a component of Red Hat Enterprise Linux 10; rust-std-static as a component of Red Hat Enterprise Linux 10; rust-std-static-aarch64-unknown-none-softfloat as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-unknown-unknown as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-wasip1 as a component of Red Hat Enterprise Linux 10; rust-std-static-x86_64-unknown-none as a component of Red Hat Enterprise Linux 10; rust-toolset as a component of Red Hat Enterprise Linux 10; rust-toolset-srpm-macros as a component of Red Hat Enterprise Linux 10; rust.src as a component of Red Hat Enterprise Linux 10; rustfmt as a component of Red Hat Enterprise Linux 10; libgit2-devel as a component of Red Hat Enterprise Linux 8; libgit2.src as a component of Red Hat Enterprise Linux 8; cargo as a component of Red Hat Enterprise Linux 9; clippy as a component of Red Hat Enterprise Linux 9; rust as a component of Red Hat Enterprise Linux 9; rust-analysis as a component of Red Hat Enterprise Linux 9; rust-analyzer as a component of Red Hat Enterprise Linux 9; rust-debugger-common as a component of Red Hat Enterprise Linux 9; rust-doc as a component of Red Hat Enterprise Linux 9; rust-gdb as a component of Red Hat Enterprise Linux 9; rust-lldb as a component of Red Hat Enterprise Linux 9; rust-src as a component of Red Hat Enterprise Linux 9; rust-std-static as a component of Red Hat Enterprise Linux 9; and 7 more
Fixed
libgit2-main@aarch64 as a component of Red Hat Hardened Images; libgit2-main@src as a component of Red Hat Hardened Images; libgit2-main@x86_64 as a component of Red Hat Hardened Images
Action
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 20 Aug 2026 · Last source change 20 Aug 2026, 19:04 UTC · CWE-295 · Improper Certificate Validation
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source ?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.FIRST · tracked since 2026-08-23
European sourceENISA EUVD · EUVD-2026-63549
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Affected versionsThe structured affected or fixed version information changed.
Before
cargo as a component of Red Hat Enterprise Linux 10; clippy as a component of Red Hat Enterprise Linux 10; rust-analyzer as a component of Red Hat Enterprise Linux 10; rust-debugger-common as a component of Red Hat Enterprise Linux 10; rust-doc as a component of Red Hat Enterprise Linux 10; rust-gdb as a component of Red Hat Enterprise Linux 10; rust-lldb as a component of Red Hat Enterprise Linux 10; rust-src as a component of Red Hat Enterprise Linux 10; rust-std-static as a component of Red Hat Enterprise Linux 10; rust-std-static-aarch64-unknown-none-softfloat as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-unknown-unknown as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-wasip1 as a component of Red Hat Enterprise Linux 10; rust-std-static-x86_64-unknown-none as a component of Red Hat Enterprise Linux 10; rust-toolset as a component of Red Hat Enterprise Linux 10; rust-toolset-srpm-macros as a component of Red Hat Enterprise Linux 10; rust.src as a component of Red Hat Enterprise Linux 10; rustfmt as a component of Red Hat Enterprise Linux 10; libgit2-devel as a component of Red Hat Enterprise Linux 8; libgit2.src as a component of Red Hat Enterprise Linux 8; cargo as a component of Red Hat Enterprise Linux 9; clippy as a component of Red Hat Enterprise Linux 9; rust as a component of Red Hat Enterprise Linux 9; rust-analysis as a component of Red Hat Enterprise Linux 9; rust-analyzer as a component of Red Hat Enterprise Linux 9; rust-debugger-common as a component of Red Hat Enterprise Linux 9; rust-doc as a component of Red Hat Enterprise Linux 9; rust-gdb as a component of Red Hat Enterprise Linux 9; rust-lldb as a component of Red Hat Enterprise Linux 9; rust-src as a component of Red Hat Enterprise Linux 9; rust-std-static as a component of Red Hat Enterprise Linux 9; and 8 more
After
cargo as a component of Red Hat Enterprise Linux 10; clippy as a component of Red Hat Enterprise Linux 10; rust-analyzer as a component of Red Hat Enterprise Linux 10; rust-debugger-common as a component of Red Hat Enterprise Linux 10; rust-doc as a component of Red Hat Enterprise Linux 10; rust-gdb as a component of Red Hat Enterprise Linux 10; rust-lldb as a component of Red Hat Enterprise Linux 10; rust-src as a component of Red Hat Enterprise Linux 10; rust-std-static as a component of Red Hat Enterprise Linux 10; rust-std-static-aarch64-unknown-none-softfloat as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-unknown-unknown as a component of Red Hat Enterprise Linux 10; rust-std-static-wasm32-wasip1 as a component of Red Hat Enterprise Linux 10; rust-std-static-x86_64-unknown-none as a component of Red Hat Enterprise Linux 10; rust-toolset as a component of Red Hat Enterprise Linux 10; rust-toolset-srpm-macros as a component of Red Hat Enterprise Linux 10; rust.src as a component of Red Hat Enterprise Linux 10; rustfmt as a component of Red Hat Enterprise Linux 10; libgit2-devel as a component of Red Hat Enterprise Linux 8; libgit2.src as a component of Red Hat Enterprise Linux 8; cargo as a component of Red Hat Enterprise Linux 9; clippy as a component of Red Hat Enterprise Linux 9; rust as a component of Red Hat Enterprise Linux 9; rust-analysis as a component of Red Hat Enterprise Linux 9; rust-analyzer as a component of Red Hat Enterprise Linux 9; rust-debugger-common as a component of Red Hat Enterprise Linux 9; rust-doc as a component of Red Hat Enterprise Linux 9; rust-gdb as a component of Red Hat Enterprise Linux 9; rust-lldb as a component of Red Hat Enterprise Linux 9; rust-src as a component of Red Hat Enterprise Linux 9; rust-std-static as a component of Red Hat Enterprise Linux 9; and 7 more · Fixed: libgit2-main@aarch64 as a component of Red Hat Hardened Images; libgit2-main@src as a component of Red Hat Hardened Images; libgit2-main@x86_64 as a component of Red Hat Hardened Images
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
CVE-2026-53583: libgit2: Inverted IP SubjectAltName Comparison in OpenSSL Backend | BlackTree
