{"id":"CVE-2026-113351","kind":"vulnerability","aliases":["CVE-2026-113351"],"related":[],"title":"libexpat: parser reset leaks memory accounting, later XML parses fail","description":"libexpat 2.7.2 through 2.9.0 contains a denial of service vulnerability because XML_ParserReset zeroes the direct byte count but never offsets tracked heap allocations. Attackers can submit a large XML document so later documents on the same reset parser fail with XML_ERROR_NO_MEMORY until it is recreated.","summary":"libexpat versions 2.7.2 through 2.9.0 fail to reset a parser's heap accounting in XML_ParserReset, so a large XML document leaves the reset parser unable to allocate memory. Later documents parsed on that same parser fail with XML_ERROR_NO_MEMORY until the parser is recreated, which is a denial of service.","severity":"high","cvss":8.2,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["c","infrastructure","libexpat","python","self-hosted"],"not_affected_if":["fresh-parser-per-document","no-untrusted-xml"],"how_to_check":"- Run `xmllint --version` or check the bundled expat version with `pkg-config --modversion expat` on Linux systems\n- Search your dependencies for libexpat, for example `ldd` output on binaries or the expat package in your OS package manager\n- Look for code that calls XML_ParserReset and reuses one parser across many documents, unknown otherwise","fix":"- Upgrade libexpat to a release later than `2.9.0` once your OS or vendor ships it, the exact fixed version is unknown from the sources\n- Until patched, recreate the parser instead of reusing it with XML_ParserReset after large documents","status":"open","published_at":"2026-10-20T11:17:19+00:00","first_seen_at":"2026-10-23T21:57:20+00:00","triaged_at":"2026-10-25T03:04:14+00:00","updated_at":"2026-10-25T03:04:14+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-25T03:04:14Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade libexpat to a release later than `2.9.0` once your OS or vendor ships it, the exact fixed version is unknown from the sources\n- Until patched, recreate the parser instead of reusing it with XML_ParserReset after large documents","reach":"network","title":"libexpat: parser reset leaks memory accounting, later XML parses fail","impact":"low","summary":"libexpat versions 2.7.2 through 2.9.0 fail to reset a parser's heap accounting in XML_ParserReset, so a large XML document leaves the reset parser unable to allocate memory. Later documents parsed on that same parser fail with XML_ERROR_NO_MEMORY until the parser is recreated, which is a denial of service.","category":"infrastructure","nicknames":[],"who_cares":["libexpat","c","python","self-hosted"],"confidence":0.6,"needs_auth":"no","worst_case":"Parser stops accepting documents until recreated, service degraded","analyst_note":"Confirm the fixed libexpat version and the affected-version range against the upstream expat advisory, since the sources list only NVD.","how_to_check":"- Run `xmllint --version` or check the bundled expat version with `pkg-config --modversion expat` on Linux systems\n- Search your dependencies for libexpat, for example `ldd` output on binaries or the expat package in your OS package manager\n- Look for code that calls XML_ParserReset and reuses one parser across many documents, unknown otherwise","needs_analyst":true,"not_affected_if":["fresh-parser-per-document","no-untrusted-xml"],"who_is_affected":"Applications and services that link libexpat 2.7.2 through 2.9.0 and parse untrusted XML with a long-lived parser that is reset and reused between documents. Systems that create a fresh parser per document, or that do not use libexpat, are not exposed to this issue.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000677,"input_tokens":3340,"output_tokens":685,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-113351':13A,16A '-2026':12A,15A '2.7.2':26B,78C '2.9.0':28B,80C 'account':6A,36B 'alloc':51B,100C 'attack':101C 'byte':93C 'c':17B 'contain':81C 'count':94C 'cve':11A,14A 'denial':74B,83C 'direct':92C 'document':44B,54B,107C,110C 'error':63B,119C 'fail':10A,29B,60B,116C 'heap':35B,99C 'host':23B 'infrastructur':18B 'larg':42B,105C 'later':7A,53B,109C 'leak':4A 'leav':45B 'libexpat':1A,19B,24B,77C 'memori':5A,52B,65B,121C 'never':96C 'offset':97C 'pars':9A,55B 'parser':2A,33B,48B,59B,68B,115C 'parserreset':39B,89C 'python':20B 'recreat':70B,125C 'reset':3A,31B,47B,114C 'self':22B 'self-host':21B 'servic':76B,85C 'submit':103C 'track':98C 'unabl':49B 'version':25B 'vulner':86C 'xml':8A,38B,43B,62B,88C,106C,118C 'zero':90C","nicknames":[],"mitigations":[],"who_affected":"Applications and services that link libexpat 2.7.2 through 2.9.0 and parse untrusted XML with a long-lived parser that is reset and reused between documents. Systems that create a fresh parser per document, or that do not use libexpat, are not exposed to this issue.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T11:17:19+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-113351","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-113351","severity":null,"published_at":"2026-10-20T11:17:19+00:00","modified_at":"2026-10-20T20:06:37+00:00","first_seen_at":"2026-10-23T21:57:20+00:00","fetched_at":"2026-10-23T22:28:58+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}