CVE-2026-54355

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th percentile of EPSS-scored CVEs). 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: epss, secondary
Elevated
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 5.3Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

MapServer is a system for developing web-based GIS applications. From 6.0 until 8.6.4, MapServer's OpenLayers HTML output for SERVICE=WMS&REQUEST=GetMap&FORMAT=application/openlayers reflects an attacker-controlled X-Forwarded-Host value received as HTTP_X_FORWARDED_HOST through msBuildOnlineResource(), processLine(), and the [mapserv_onlineresource] substitution in src/maputil.c and src/maptemplate.c without escaping it for a single-quoted JavaScript string. When the deployment trusts the forwarded header and does not configure a fixed ows_onlineresource or MS_ONLINERESOURCE value, embedded single quotes can escape the generated URL string. An unauthenticated attacker can craft a URL that executes arbitrary JavaScript in the MapServer site origin when opened by a victim, enabling access to sessions or tokens, same-origin data and requests, and actions as the victim. This issue is fixed in version 8.6.4.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100CISA SSVC

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 computed
Severity53% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
40th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 17, 2026

Last Modified

September 30, 2026

Advisory Details (7)

Auto-updated Sep 17, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr, github_commit, github_release, github.
generic

MapServer 8.6 Changelog — MapServer 8.6.6 documentation

https://mapserver.org/development/changelog/changelog-8-6.html#changelog-8-6
github_release Patch Available

MapServer 8.6.4

Patch available: MapServer/MapServer rel-8-6-4

https://github.com/MapServer/MapServer/releases/tag/rel-8-6-4
github_commit Patch Available

commit ff17ef190caa (MapServer/MapServer)

Patch available: MapServer/MapServer rel-8-6-4 (contains commit ff17ef190caa)

https://github.com/MapServer/MapServer/commit/ff17ef190caaeaa9002ac3d1c7969ec5315c345e
github_commit

commit edc1033c7963 (MapServer/MapServer)

Fix landed in MapServer/MapServer commit edc1033c7963 — awaiting tagged release

https://github.com/MapServer/MapServer/commit/edc1033c7963fcffd160d85cf430f49aaf4a1374
github_pr Patch Available

[Backport branch-8-6] WMS OpenLayers output: properly escape mapserv_onlineresource

Patch available: MapServer/MapServer rel-8-6-4 (PR #7518 merged 2026-06-01)

https://github.com/MapServer/MapServer/pull/7518
github_pr

WMS OpenLayers output: properly escape mapserv_onlineresource

Fix merged in MapServer/MapServer PR #7517 on 2026-05-31 — awaiting tagged release

https://github.com/MapServer/MapServer/pull/7517
github Patch Available🟡 PoC Available

MapServer 8.6.3: Reflected XSS in OpenLayers HTML Output via `HTTP_X_FORWARDED_HOST` · Advisory · MapServer/MapServer · GitHub

https://github.com/MapServer/MapServer/security/advisories/GHSA-xqj6-vjqr-33vv

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.0.0-3 ... 8.6.6-1~bpo13+1 (53 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.4.0-4 ... 8.6.6-1~bpo13+1 (23 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
mapserver8.4.0-4 ... 8.6.4-1~bpo13+1 (16 versions)
  • every version up to 8.6.4-1: fixed in 8.6.4-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 33× 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.

  1. 2026-10-05 03:07 UTCEG score recompute
  2. 2026-10-04 23:22 UTCEPSS rescore
  3. 2026-10-04 00:29 UTCEG score recompute
  4. 2026-10-03 14:26 UTCEPSS rescore
  5. 2026-10-02 22:09 UTCEG score recompute
  6. 2026-10-02 17:56 UTCEPSS rescore
  7. 2026-10-01 19:50 UTCEPSS rescore
  8. 2026-09-30 17:27 UTCEG score recompute
  9. 2026-09-30 15:03 UTCEPSS rescore
  10. 2026-09-30 09:08 UTCEG score recompute
  11. 2026-09-29 15:22 UTCEPSS rescore
  12. 2026-09-29 06:45 UTCEG score recompute
  13. 2026-09-28 13:51 UTCEPSS rescore
  14. 2026-09-28 04:26 UTCEG score recompute
  15. 2026-09-27 13:48 UTCEPSS rescore
  16. 2026-09-27 02:06 UTCEG score recompute
  17. 2026-09-26 15:59 UTCEPSS rescore
  18. 2026-09-25 23:47 UTCEG score recompute
  19. 2026-09-24 21:24 UTCEG score recompute
  20. 2026-09-24 20:57 UTCEG score recompute
  21. 2026-09-24 14:04 UTCEPSS rescore
  22. 2026-09-24 11:18 UTCEG score recompute
  23. 2026-09-23 17:54 UTCEPSS rescore
  24. 2026-09-23 08:59 UTCEG score recompute
  25. 2026-09-22 06:39 UTCEG score recompute
Show 8 more
  1. 2026-09-21 04:19 UTCEG score recompute
  2. 2026-09-20 20:16 UTCEPSS rescore
  3. 2026-09-20 01:59 UTCEG score recompute
  4. 2026-09-18 23:39 UTCEG score recompute
  5. 2026-09-18 19:28 UTCEPSS rescore
  6. 2026-09-17 21:20 UTCEG score recompute
  7. 2026-09-17 20:34 UTCEG score recompute
  8. 2026-09-17 20:34 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-54355?
CVE-2026-54355 is a medium vulnerability published on September 17, 2026. MapServer is a system for developing web-based GIS applications. From 6.0 until 8.6.4, MapServer's OpenLayers HTML output for SERVICE=WMS&REQUEST=GetMap&FORMAT=application/openlayers reflects an attacker-controlled X-Forwarded-Host value received as HTTPXFORWARDEDHOST through…
When was CVE-2026-54355 disclosed?
CVE-2026-54355 was first published on September 17, 2026, with the most recent update on September 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54355 actively exploited?
CVE-2026-54355 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54355?
CVE-2026-54355 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54355?
A fix for CVE-2026-54355 is available: update to the fixed version the vendor names in its advisory.

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