CVE-2018-20843 — In libexpat in Expat before 2

In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).

01What is this vulnerability?

In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-06-24T17:15:09.980
• Last modified: 2026-10-14T07:16:43.890

09References

• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00039.html
• bugs.chromium.org — https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5226
• github.com — https://github.com/libexpat/libexpat/blob/R_2_2_7/expat/Changes
• github.com — https://github.com/libexpat/libexpat/issues/186
• github.com — https://github.com/libexpat/libexpat/pull/262
• github.com — https://github.com/libexpat/libexpat/pull/262/commits/11f8838bf99ea0a6f0b76f9760…
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2019/06/msg00028.html
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• seclists.org — https://seclists.org/bugtraq/2019/Jun/39