CVE-2021-47527: serial: core: fix transmit-buffer reset and memleak
Vulnerability summary
CVE-2021-47527 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 16.5% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 3Timeline
- 24-05-2024PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: serial: core: fix transmit-buffer reset and memleak Commit 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") converted serial core to use tty_port_close() but failed to notice that the transmit buffer still needs to be freed on final close. Not freeing the transmit buffer means that the buffer is no longer cleared on next open so that any ioctl() waiting for the buffer to drain might wait indefinitely (e.g. on termios changes) or that stale data can end up being transmitted in case tx is restarted. Furthermore, the buffer of any port that has been opened would leak on driver unbind. Note that the port lock is held when clearing the buffer pointer due to the ldisc race worked around by commit a5ba1d95e46e ("uart: fix race between uart_put_char() and uart_shutdown()"). Also note that the tty-port shutdown() callback is not called for console ports so it is not strictly necessary to free the buffer page after releasing the lock (cf. d72402145ace ("tty/serial: do not free trasnmit buffer page under port lock")).
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.25%
Chance of exploitation in the next 30 days
Percentile
17%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.25% 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: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu87 products
- linux< 4.15.0-169.177 | < 5.4.0-100.113
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 4.15.0-1121.129 | < 5.4.0-1066.69
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < 011f6c92b5bf6e1fbfdedc8b5232f64c1c493206 | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < e74d9663fd57640fc3394abb5c76fa95b9cc2f2e | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < 1179b168fa3f3a6aae3bd140000455a0e58457db | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < c5da8aa441053958594f94254592bb41264bdfbf | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < e1722acf4f0d4d67b60f57e08ce16f8b66cd4b8f | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < 64e491c1634b73d3bddc081d08620bdc92ab2c12 | ≥ 761ed4a94582ab291aa24dcbea4e01e8936488c8, < 00de977f9e0aa9760d9a79d1e41ff780f74e3424 | 4.9
- linux_kernel≥ 4.9, < 4.9.292 | ≥ 4.10, < 4.14.257 | ≥ 4.15, < 4.19.220 | ≥ 4.20, < 5.4.164 | ≥ 5.5, < 5.10.84 | ≥ 5.11, < 5.15.7 | 5.16:rc1 | 5.16:rc2 | 5.16:rc3
Debian1 product
- linux< 5.15.15-1
3 vendors · 90 products
