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CVE-2026-23557

Xenstored DoS via XS_RESET_WATCHES command

6.5 MediumFix available

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.16%Up 0.1 points since May 20, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.5

Xenstored DoS via XS_RESET_WATCHES command

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
CVE-2026-23557
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-617
Updated
2026-11-02
EUVDEUVD-2026-30925 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
EUVD-2026-30925
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-9879-vj7m-r497 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction...

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
GHSA-9879-vj7m-r497
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-617
Updated
2026-11-02
NVD 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
CVE-2026-23557
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-617
Updated
2026-11-02
OSVALPINE-CVE-2026-23557 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering.

In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
ALPINE-CVE-2026-23557
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2026-23557 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering. In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
DEBIAN-CVE-2026-23557
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
Show 9 moreShow less
OSVUBUNTU-CVE-2026-23557 6.5

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering. In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Record
UBUNTU-CVE-2026-23557
CVSS 3.1
6.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2026:10660-1 No score

xen-4.21.1_04-1.1 on GA media

These are all security issues fixed in the xen-4.21.1_04-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:10660-1
Updated
2026-11-02
OSVSUSE-SU-2026:1645-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2025-54505: floating point divider state sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:1645-1
Updated
2026-11-02
OSVSUSE-SU-2026:1657-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2025-54505: floating point divider state sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:1657-1
Updated
2026-11-02
OSVSUSE-SU-2026:1692-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2025-54505: Floating Point Divider State Sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:1692-1
Updated
2026-11-02
OSVSUSE-SU-2026:1743-1 No score

Security update for xen

This update for xen fixes the following issues:

  • Update to Xen 4.20.3 bug fix release (bsc#1027519) (jsc#PED-8907).
  • CVE-2025-54505: Floating Point Divider State Sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:1743-1
Updated
2026-11-02
OSVSUSE-SU-2026:1998-1 No score

Security update for xen

This update for xen fixes the following issue

  • CVE-2025-54518: AMD-SN-7052: CPU OP Cache Corruption (bsc#1264066).
Record
SUSE-SU-2026:1998-1
Updated
2026-11-02
OSVSUSE-SU-2026:2066-1 No score

Security update for xen

This update for xen fixes the following issues

  • CVE-2025-54505: Floating Point Divider State Sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2025-54518: AMD-SN-7052: CPU OP Cache Corruption (bsc#1264066).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:2066-1
Updated
2026-11-02
OSVSUSE-SU-2026:2102-1 No score

Security update for xen

This update for xen fixes the following issues

  • CVE-2025-54505: Floating Point Divider State Sampling on AMD CPUs AMD-SN-7053 (bsc#1262428).
  • CVE-2025-54518: AMD-SN-7052: CPU OP Cache Corruption (bsc#1264066).
  • CVE-2026-23557: Xenstored DoS via XS_RESET_WATCHES command (bsc#1262178).
  • CVE-2026-23558: grant table v2 race in status page mapping (bsc#1262180).
Record
SUSE-SU-2026:2102-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
xen
Alpine:v3.20
 4.2.0 up to 4.18.5-r7
4.18.5-r7
xen
Alpine:v3.21
 4.2.0 up to 4.19.5-r2
4.19.5-r2
xen
Alpine:v3.22
 4.2.0 up to 4.20.3-r2
4.20.3-r2
xen
Alpine:v3.23
 4.2.0 up to 4.20.3-r2
4.20.3-r2
xen
Alpine:v3.24
 4.2.0 up to 4.21.1-r3
4.21.1-r3
xen
Debian:12
 before 4.17.7-0+deb12u1, plus listed versions
4.17.1+2-gb773c48e36-14.17.2+55-g0b56bed864-14.17.2+76-ge1f9cb16e2-14.17.2+76-ge1f9cb16e2-1~deb12u14.17.2-1
Show 9 moreShow less
4.17.3+10-g091466ba55-14.17.3+10-g091466ba55-1.14.17.3+10-g091466ba55-1.1~exp14.17.3+10-g091466ba55-1.1~exp24.17.3+10-g091466ba55-1~deb12u14.17.3+36-g54dacb5c02-14.17.5+23-ga4e5191dc0-14.17.5+23-ga4e5191dc0-1+deb12u14.17.5+72-g01140da4e8-1
4.17.7-0+deb12u1
xen
Debian:13
 before 4.20.3+127-gc42374a105-0+deb13u1, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+37-g61ff35323e-0+deb13u14.20.2+37-g61ff35323e-14.20.2+7-g1badcf5035-0+deb13u14.20.2+7-g1badcf5035-14.20.2+7-g1badcf5035-2
4.20.3+127-gc42374a105-0+deb13u1
xen
Debian:14
 before 4.20.3+127-gc42374a105-1, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+37-g61ff35323e-14.20.2+7-g1badcf5035-14.20.2+7-g1badcf5035-2
4.20.3+127-gc42374a105-1
xen
Ubuntu:16.04:LTS
 All versions, plus listed versions
4.5.1-0ubuntu14.5.1-0ubuntu24.6.0-1ubuntu14.6.0-1ubuntu24.6.0-1ubuntu4
Show 7 moreShow less
4.6.0-1ubuntu4.14.6.0-1ubuntu4.24.6.0-1ubuntu4.34.6.5-0ubuntu14.6.5-0ubuntu1.14.6.5-0ubuntu1.24.6.5-0ubuntu1.4
 None known
xen
Ubuntu:18.04:LTS
 All versions, plus listed versions
4.9.0-0ubuntu34.9.0-0ubuntu44.9.2-0ubuntu1
 None known
Show 7 moreShow less
Affected packages
PackageAffectedFixed
xen
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.9.2-0ubuntu24.9.2-0ubuntu64.9.2-0ubuntu74.11.3+24-g14b62ab3e5-1ubuntu14.11.3+24-g14b62ab3e5-1ubuntu24.11.3+24-g14b62ab3e5-1ubuntu2.24.11.3+24-g14b62ab3e5-1ubuntu2.3
 None known
xen
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.11.4+24-gddaaccbbab-1ubuntu24.16.0-1~ubuntu24.16.0-1~ubuntu2.1
 None known
xen
Ubuntu:24.04:LTS
 All versions, plus listed versions
4.17.2-14.17.2+55-g0b56bed864-14.17.2+76-ge1f9cb16e2-14.17.2+76-ge1f9cb16e2-1ubuntu14.17.3+10-g091466ba55-14.17.3+10-g091466ba55-1.1ubuntu24.17.3+10-g091466ba55-1.1ubuntu3
 None known
xen
Ubuntu:25.10
 All versions, plus listed versions
4.20.0-1ubuntu14.20.0+68-g35cb38b222-1
 None known
xen
Ubuntu:26.10
 All versions, plus listed versions
4.20.2+7-g1badcf5035-2build24.20.2+37-g61ff35323e-1ubuntu14.20.3+127-gc42374a105-1
 None known
xen
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+7-g1badcf5035-24.20.2+7-g1badcf5035-2build2
 None known
xen
openSUSE:Tumbleweed
 before 4.21.1_04-1.1
4.21.1_04-1.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-23557 is a medium vulnerability (CVSS 6.5) in Xen, published April 28, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 4th percentile. Fixed in xen 4.18.5-r7.

References

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