CVE-2018-16840: canonical ubuntu_linux Use After Free
Vulnerability summary
CVE-2018-16840 is a critical (CVSS 9.8) Use After Free vulnerability in canonical ubuntu_linux. EPSS estimates a 3.40% chance of exploitation in the next 30 days, higher than 88.8% of scored vulnerabilities.
Not severe (CVSS 4.3, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 6 · Related 6Timeline
- 31-10-2018PublishedVulnerability first disclosed.
- 16-04-2026Last modifiedVulnerability information updated.
Description
A heap use-after-free flaw was found in curl versions from 7.59.0 through 7.61.1 in the code related to closing an easy handle. When closing and cleaning up an 'easy' handle in the `Curl_close()` function, the library code first frees a struct (without nulling the pointer) and might then subsequently erroneously write to a struct field within that already freed struct.
CVSS metrics
8 scores · 5 sources · 3 versions- OSV · AlpineEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST4.3MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HDiffers
EPSS trend
Probability
3.40%
Chance of exploitation in the next 30 days
Percentile
89%
Versus all other CVEs
30-day change
No change 0.00 pp
From 3.40% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Alpine1 product
- curl≥ 7.59.0, < 7.62.0-r0 | ≥ 7.59.0, < 7.61.1-r1
Canonical1 product
- ubuntu_linuxEOL14.04 | 16.04 | 18.04 | 18.10
Debian1 product
- curl< 7.62.0-1
Haxx1 product
- curl≥ 7.59.0, < 7.62.0
The curl project1 product
- curlfrom 7.59.0 to 7.61.1
Ubuntu1 product
- curl< 7.58.0-2ubuntu3.3
6 vendors · 6 products
References
11 links- bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16840X Refsource CONFIRMIssue TrackingThird Party Advisory
- github.com/curl/curl/commit/81d135d67155c5295b1033679c606165d4e28f3fX Refsource CONFIRMPatchThird Party Advisory
