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CVE-2026-2436

Libsoup: libsoup: denial of service via use-after-free in soupserver during tls handshake

6.5 MediumFix available

CVE-2026-2436 is a medium vulnerability (CVSS 6.5) in Gnome Libsoup, published March 26, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.46%, the 39th percentile. Fixed in libsoup 3.4.4-15.

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
High

Exploit likelihood

0.46%Up 0.4 points since Mar 27, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.5

Libsoup: libsoup: denial of service via use-after-free in soupserver during tls handshake

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
CVE-2026-2436
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-825
Updated
2026-11-02
EUVDEUVD-2026-16342 6.5

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
EUVD-2026-16342
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-wpfw-5xvc-wq9w 6.5

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free...

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
GHSA-wpfw-5xvc-wq9w
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-825
Updated
2026-11-02
NVD 6.5

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
CVE-2026-2436
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-825
Updated
2026-11-02
OSVDEBIAN-CVE-2026-2436 8.2

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
DEBIAN-CVE-2026-2436
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-02
OSVOESA-2026-2666 7.5

libsoup3 security update

Libsoup is an HTTP library implementation in C. It was originally part of a SOAP (Simple Object Access Protocol) implementation called Soup, but the SOAP and non-SOAP parts have now been split into separate packages.

Security Fix(es):

A flaw was found in libsoup. The SoupWebsocketConnection may accept a large WebSocket message, which may cause libsoup to allocate memory and lead to a denial of service (DoS).(CVE-2025-32049)

A flaw was found in libsoup. The libsoup append_param_quoted() function may contain an overflow bug resulting in a buffer under-read.(CVE-2025-32050)

A flaw was found in libsoup. The libsoup soup_uri_decode_data_uri() function may crash when processing malformed data URI. This flaw allows an attacker to cause a denial of service (DoS).(CVE-2025-32051)

A flaw was found in libsoup. The implementation of HTTP range requests is vulnerable to a resource consumption attack. This flaw allows a malicious client to request the same range many times in a single HTTP request, causing the server to use large amounts of memory. This does not allow for a full denial of service.(CVE-2025-32907)

A flaw was found in SoupServer. This HTTP request smuggling vulnerability occurs because SoupServer improperly handles requests that combine Transfer-Encoding: chunked and Connection: keep-alive headers. A remote, unauthenticated client can exploit this by sending specially crafted requests, causing SoupServer to fail to close the connection as required by RFC 9112. This allows the attacker to smuggle additional requests over the persistent connection, leading to unintended request processing and potential denial-of-service (DoS) conditions.(CVE-2026-1760)

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.(CVE-2026-2436)

A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic. The soup_message_headers_append_common() function in libsoup/soup-message-headers.c unconditionally appends each header value without validating for duplicate or conflicting Content-Length fields. This allows an attacker to send HTTP requests containing multiple Content-Length headers with differing values.(CVE-2026-2708)

Record
OESA-2026-2666
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 5 moreShow less
OSVOESA-2026-2667 7.5

libsoup3 security update

Libsoup is an HTTP library implementation in C. It was originally part of a SOAP (Simple Object Access Protocol) implementation called Soup, but the SOAP and non-SOAP parts have now been split into separate packages.

Security Fix(es):

A flaw was found in libsoup. The SoupWebsocketConnection may accept a large WebSocket message, which may cause libsoup to allocate memory and lead to a denial of service (DoS).(CVE-2025-32049)

A flaw was found in libsoup. The implementation of HTTP range requests is vulnerable to a resource consumption attack. This flaw allows a malicious client to request the same range many times in a single HTTP request, causing the server to use large amounts of memory. This does not allow for a full denial of service.(CVE-2025-32907)

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.(CVE-2026-2436)

A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic. The soup_message_headers_append_common() function in libsoup/soup-message-headers.c unconditionally appends each header value without validating for duplicate or conflicting Content-Length fields. This allows an attacker to send HTTP requests containing multiple Content-Length headers with differing values.(CVE-2026-2708)

Record
OESA-2026-2667
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVROOT-OS-DEBIAN-12-CVE-2026-2436 8.2

CVE-2026-2436 in libsoup2.4 - Patched by Root

Root has patched CVE-2026-2436 in the libsoup2.4 package for Root:Debian:12. Multiple fixed versions available.

Record
ROOT-OS-DEBIAN-12-CVE-2026-2436
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-02
OSVROOT-OS-DEBIAN-13-CVE-2026-2436 8.2

CVE-2026-2436 in libsoup3 - Patched by Root

Root has patched CVE-2026-2436 in the libsoup3 package for Root:Debian:13. Multiple fixed versions available.

Record
ROOT-OS-DEBIAN-13-CVE-2026-2436
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-2436 6.5

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
UBUNTU-CVE-2026-2436
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-03
OSVAZL-81519 No score

CVE-2026-2436 affecting package libsoup for versions less than 3.4.4-15

A flaw was found in libsoup's SoupServer. A remote attacker could exploit a use-after-free vulnerability where the soup_server_disconnect() function frees connection objects prematurely, even if a TLS handshake is still pending. If the handshake completes after the connection object has been freed, a dangling pointer is accessed, leading to a server crash and a Denial of Service.

Record
AZL-81519
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libsoup
Azure Linux:3
before 3.4.4-15
3.4.4-15
libsoup2.4
Debian:12
All versions, plus listed versions
2.74.3-12.74.3-1+deb12u12.74.3-102.74.3-10.12.74.3-11
Show 11 moreShow less
2.74.3-22.74.3-32.74.3-3.1~exp12.74.3-3.1~exp22.74.3-3.1~exp32.74.3-52.74.3-62.74.3-72.74.3-82.74.3-8.12.74.3-9
None known
libsoup2.4
Debian:13
All versions, plus listed versions
2.74.3-10.12.74.3-11
None known
libsoup3
Debian:12
All versions, plus listed versions
3.2.2-23.2.3-0+deb12u13.2.3-0+deb12u23.3.1-13.4.0-1
Show 33 moreShow less
3.4.1-13.4.2-13.4.2-23.4.2-33.4.2-43.4.3-13.4.4-13.4.4-23.4.4-33.4.4-43.4.4-53.5.2-13.6.0-13.6.0-23.6.0-33.6.0-43.6.1-13.6.4-13.6.4-23.6.4-33.6.5-13.6.5-23.6.5-33.6.5-43.6.5-53.6.5-63.6.5-73.6.5-83.6.5-93.6.6-13.8.0-13.8.0-23.8.0-3
None known
libsoup3
Debian:13
All versions, plus listed versions
3.6.5-33.6.5-43.6.5-53.6.5-63.6.5-7
Show 6 moreShow less
3.6.5-83.6.5-93.6.6-13.8.0-13.8.0-23.8.0-3
None known
libsoup3
openEuler:24.03-LTS-SP1
before 3.4.5-19.oe2403sp1
3.4.5-19.oe2403sp1
libsoup3
openEuler:24.03-LTS-SP3
before 3.4.5-19.oe2403sp3
3.4.5-19.oe2403sp3
libsoup2.4
Root:Debian:12
before 2.74.3-1+deb12u1.aikido.3
2.74.3-1+deb12u1.aikido.32.74.3-1+deb12u1.aikido.42.74.3-1+deb12u1.aikido.5
rootio-libsoup2.4
Root:Debian:12
before 2.74.3-1+deb12u1.aikido.3
2.74.3-1+deb12u1.aikido.32.74.3-1+deb12u1.aikido.42.74.3-1+deb12u1.aikido.5
libsoup3
Root:Debian:13
before 3.6.5-3.aikido.4
3.6.5-3.aikido.43.6.5-3.aikido.33.6.5-3.root.io.13.6.5-3.root.io.23.6.5-3.aikido.53.6.5-3.aikido.63.6.5-3.aikido.73.6.5-3.aikido.8
Show 6 moreShow less
Affected packages
PackageAffectedFixed
rootio-libsoup3
Root:Debian:13
before 3.6.5-3.aikido.4
3.6.5-3.aikido.43.6.5-3.aikido.33.6.5-3.root.io.13.6.5-3.root.io.23.6.5-3.aikido.53.6.5-3.aikido.63.6.5-3.aikido.73.6.5-3.aikido.8
libsoup3
Ubuntu:Pro:22.04:LTS
All versions, plus listed versions
3.0.4-23.0.4-33.0.5-13.0.7-0ubuntu13.0.7-0ubuntu1+esm1
Show 9 moreShow less
3.0.7-0ubuntu1+esm23.0.7-0ubuntu1+esm33.0.7-0ubuntu1+esm43.0.7-0ubuntu1+esm53.0.7-0ubuntu1+esm63.0.7-0ubuntu1+esm73.0.7-0ubuntu1+esm83.0.7-0ubuntu1+esm93.0.7-0ubuntu1+esm10
None known
libsoup3
Ubuntu:24.04:LTS
All versions, plus listed versions
3.4.2-43.4.4-13.4.4-23.4.4-43.4.4-5
Show 12 moreShow less
3.4.4-5build13.4.4-5build23.4.4-5ubuntu0.13.4.4-5ubuntu0.23.4.4-5ubuntu0.33.4.4-5ubuntu0.43.4.4-5ubuntu0.53.4.4-5ubuntu0.63.4.4-5ubuntu0.73.4.4-5ubuntu0.83.4.4-5ubuntu0.93.4.4-5ubuntu0.10
None known
libsoup3
Ubuntu:25.10
All versions, plus listed versions
3.6.5-13.6.5-1ubuntu13.6.5-33.6.5-43.6.5-4ubuntu0.13.6.5-4ubuntu0.2
None known
libsoup3
Ubuntu:26.10
All versions, plus listed versions
3.6.6-13.6.6-1ubuntu33.6.6-1ubuntu3.1
None known
libsoup3
Ubuntu:26.04:LTS
All versions, plus listed versions
3.6.5-43.6.5-53.6.5-63.6.5-73.6.5-93.6.6-13.6.6-1ubuntu0.13.6.6-1ubuntu0.2
None known

History

History
WhenChangedSources
2026-11-03affected, factsOSV
2026-11-02createdCVE List, EUVD, GitHub Advisories, NVD, OSV

References

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