Description
A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 13 | libsoup3 +1 | No fix yet | — |
| Debian 12 | libsoup3 +1 | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | libsoup3 +1 | No fix yet | — |
| Ubuntu 26.04 LTS | libsoup3 | No fix yet | — |
| Ubuntu 24.04 LTS | libsoup3 +1 | No fix yet | — |
| Ubuntu 22.04 LTS | libsoup2.4 | No fix yet | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | libsoup2.4 | No fix yet | — |
| Ubuntu Pro 22.04 LTS | libsoup3 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | libsoup2.4 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | libsoup2.4 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | libsoup2.4 | No fix yet | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | libsoup +2 | 2.72.0-6.amzn2023.0.16 | ALAS2023-2026-3212 |
| Amazon Linux 2023 | libsoup3 +2 | 3.7.3-1.amzn2023 | ALAS2023-2026-3421, ALAS2023-2026-3240 |
| Amazon Linux 2 | libsoup +1 | 2.56.0-6.amzn2.0.9 | ALAS2-2026-3970 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | libsoup | No fix yet | — |
Advisories 4
- ALAS2023-2026-3421 Important: libsoup3 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Nov 12, 2026
- ALAS2023-2026-3240 Moderate: libsoup3 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2-2026-3970 Moderate: libsoup security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Oct 12, 2026
- ALAS2023-2026-3212 Important: libsoup security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 12, 2026
References
- https://access.redhat.com/security/cve/CVE-2026-66338 vdb-entry
- RHBZ#2506950 issue-tracking