How severe is CVE-2011-2536?

CVE-2011-2536 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-2011-2536 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2011-2536?

CVE-2011-2536 primarily affects Digium Asterisk. In total, 198 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2011-2536?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2011-2536 published?

CVE-2011-2536 was published on 2011-07-06 and last updated on 2026-06-16.

CVE-2011-2536

CVE-2011-2536 is a medium-severity vulnerability in Digium Asterisk with a CVSS 2.0 base score of 5.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-200.

Key facts

Severity: Medium (CVSS 2.0 base score 5.0)
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-200
Affected product: Digium Asterisk
Published: 2011-07-06
Last modified: 2026-06-16

Description

chan_sip.c in the SIP channel driver in Asterisk Open Source 1.4.x before 1.4.41.2, 1.6.2.x before 1.6.2.18.2, and 1.8.x before 1.8.4.4, and Asterisk Business Edition C.3.x before C.3.7.3, disregards the alwaysauthreject option and generates different responses for invalid SIP requests depending on whether the user account exists, which allows remote attackers to enumerate account names via a series of requests.

Frequently asked questions

What is CVE-2011-2536?: chan_sip.c in the SIP channel driver in Asterisk Open Source 1.4.x before 1.4.41.2, 1.6.2.x before 1.6.2.18.2, and 1.8.x before 1.8.4.4, and Asterisk Business Edition C.3.x before C.3.7.3, disregards the alwaysauthreject option and generates different responses for invalid SIP requests depending on whether the user account exists, which allows remote attackers to enumerate account names via a series of requests.
How severe is CVE-2011-2536?: CVE-2011-2536 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-2011-2536 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2011-2536?: CVE-2011-2536 primarily affects Digium Asterisk. In total, 198 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2011-2536?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2011-2536 published?: CVE-2011-2536 was published on 2011-07-06 and last updated on 2026-06-16.

References

Affected products (198)

cpe:2.3:a:digium:asterisk:1.8.0:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:beta1:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:beta2:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:beta3:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:beta4:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:beta5:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:rc2:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:rc3:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:rc4:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.0:rc5:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.1:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.1:rc1:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.1.1:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.1.2:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.2:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.2.1:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.2.2:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.2.3:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.2.4:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3:rc1:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3:rc2:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3:rc3:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3.1:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3.2:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.3.3:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4:rc1:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4:rc2:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4:rc3:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4.1:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4.2:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.8.4.3:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:*:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc2:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc3:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc4:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc5:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc6:*:*:*:*:*:*
cpe:2.3:a:digium:asterisk:1.6.2.0:rc7:*:*:*:*:*:*

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