CVE-2026-37231: FlexRIC v2.0.0 uses a uint16_t counter for xapp_id assignment but stores the value in uint32_t message fields

This week

HIGH 7.5REMOTEDOWNGRADE

CVE-2026-37231 is a high-severity flaw (CVSS 7.5) affecting flexric. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FlexRIC v2.0.0 uses a uint16_t counter for xapp_id assignment but stores the value in uint32_t message fields. After 65,530+ E42_SETUP_REQUESTs, the 16-bit counter wraps around and produces duplicate xapp_ids. The iApp (port 36422) crashes when attempting to register a duplicate ID in its internal data structure. A remote attacker can trigger this by repeatedly connecting and requesting new xApp registrations.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-191
Published	2026-06-01
Last modified	2026-07-22

Publisher (CNA): MITRE · Vendor: mosaic5g

Last updated 2026-07-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-01 19:16 UTCPublished CVE record published
2026-07-22 07:10 UTCUpdated Record last modified

mosaic5g flexric DOWNGRADE

Affected: 2.0.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy flexric || rpm -q flexric || flexric --version

2. No fixed release: DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison flexric sudo apt install flexric=<VERSION_BEFORE_2.0.0> sudo apt-mark hold flexric

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list flexric sudo dnf downgrade flexric-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add flexric

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-37231?

flexric: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-37231 being exploited?

CVE-2026-37231 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-37231 affect?

CVE-2026-37231 affects flexric. Severity is high (CVSS 7.5). FlexRIC v2.0.0 uses a uint16_t counter for xapp_id assignment but stores the value in uint32_t message fields. After 65,530+ E42_SETUP_REQUESTs, the 16-bit counter wraps around and produces duplicate xapp_ids. The iApp (port 36422) crashes

How urgent is CVE-2026-37231?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-37234 HIGH 8.2 DOWNGRADE FlexRIC v2.0.0 allows a single SCTP connection to bind multiple xapp_ids by sending multiple E42_SETUP_REQUEST
CVE-2026-37226 HIGH 7.5 DOWNGRADE FlexRIC v2.0.0 crashes when the iApp receives an E42_RIC_SUBSCRIPTION_REQUEST referencing a non-existent E2 No
CVE-2026-37228 HIGH 7.5 DOWNGRADE FlexRIC v2.0.0 contains a reachable assertion in e2ap_recv_sctp_msg() (src/lib/ep/e2ap_ep.c)
CVE-2026-37229 HIGH 7.5 DOWNGRADE FlexRIC v2.0.0 contains a reachable assertion in e2ap_create_pdu() triggered when ASN.1 PER decoding fails
CVE-2026-37230 HIGH 7.5 DOWNGRADE FlexRIC v2.0.0 crashes when the near-RT RIC receives a RIC_INDICATION message with a ran_func_id that does not

References

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