A cross-site scripting vulnerability in queryparser/termgenerator_internal.cc in Xapian xapian-core before 2.1.0 and before 1.4.32 exists due to incomplete HTML escaping by Xapian::MSet::snippet(). NOTE: this issue exists because of a missed corner case of CVE-2018-0499.
CVE-2026-77643
MEDIUMPre-NVD 4.44.4
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 4.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
4.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 4.4Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 4.4
- EG Score
- 4.4(low)
- EG Risk
- 24(Track)EG Risk 24/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity44% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
August 20, 2026
Last Modified
August 20, 2026
Advisory Details (3)
Auto-updated Aug 20, 2026🔬 Proof of concept available. Patch available.
generic
SecurityFixes/2018-07-02 – Xapian
https://trac.xapian.org/wiki/SecurityFixes/2018-07-02#a2026-08-13updategeneric🟡 PoC Available
MSet::snippet() returns unescaped text when hi_start and hi_end are both empty
https://lists.xapian.org/pipermail/xapian-devel/2026-August/003429.htmlgeneric Patch Available
#1144490 - libxapian30: previously missed corner case of CVE-2018-0499 - Debian Bug report logs
https://bugs.debian.org/1144490Vendor Advisories for CVE-2026-77643(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 3× in last 7d / 3× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-20 22:24 UTCEG score recompute
- 2026-08-20 21:32 UTCEG score recompute
- 2026-08-20 21:31 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(4)
What is CVE-2026-77643?
CVE-2026-77643 is a medium vulnerability published on August 20, 2026. A cross-site scripting vulnerability in queryparser/termgenerator_internal.cc in Xapian xapian-core before 2.1.0 and before 1.4.32 exists due to incomplete HTML escaping by Xapian::MSet::snippet(). NOTE: this issue exists because of a missed corner case of CVE-2018-0499.
When was CVE-2026-77643 disclosed?
CVE-2026-77643 was first published in the National Vulnerability Database on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-77643?
CVE-2026-77643 has a CVSS v3 base score of 4.4 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-77643?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77643, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-77643
Is Your Infrastructure Affected by CVE-2026-77643?
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